1. Technical Field
The present invention relates generally to medical devices, and more particularly, to an endobronchial blocking device for use in isolating a lung or a portion of a lung.
2. Background Information
Patients who are critically ill or undergoing surgical procedures involving the lungs (thoracic surgery) frequently require a lung, or a portion of a lung, to be isolated from mechanical ventilation. The lungs are located in the chest cavity and bounded by the chest wall and the diaphragm, a thin muscular membrane. The lungs are held next to the chest wall by negative pressure and a thin fluid layer. The space of opposition is the pleural space. The lungs comprise the trachea, an air conduit, and the lung tissue which abuts against the chest wall. The trachea divides in the chest cavity into two separate air conduits, a right-sided air conduit (the right mainstem bronchus) and a left-sided air conduit (the left mainstem bronchus).
Ventilation is a physiologic process which supplies oxygen to the body and removes carbon dioxide, a gaseous waste product. Ventilation is provided by the rhythmic back and forth motion of air in the trachea, caused by the rhythmic contraction and relaxation of the diaphragm. In surgical patients and in the critically ill, ventilation can be assisted by utilizing a mechanical ventilator connected to an endotracheal tube. An endotracheal tube is a balloon-tipped single or double-lumen catheter that is open at both ends, and positioned in the mid-tracheal region.
Isolation of ventilation is commonly required in medical procedures. For example, in thoracic surgery the chest wall is incised, the lung opened and the pleural space entered. As a result, the lung will collapse, and ventilation can escape. Ventilation to the non-operative lung must be isolated before opening the operative lung segment. If ventilation is not isolated before beginning the thoracic surgery, a risk of harm to the patient exists due to the escape of ventilation through the surgical lung opening. Other conditions may also require isolation from mechanical ventilation. These conditions include the isolation of a diseased portion of the lung, infections of the lung (pneumonia), bleeding in the lungs (hemoptysis), and the presence of a non-surgical opening into the pleural space (pneumothorax).
Double lumen endotracheal tubes have long been used to achieve isolation of ventilation. A double lumen endotracheal tube generally comprises two endotracheal tubes of unequal length fused together, and incorporates two balloons. One balloon envelopes the tracheal position of the two fused endotracheal tubes (the tracheal balloon), and the second balloon envelopes the longer tube portion and extends into either the right or left mainstem bronchus (the bronchial balloon). The double lumen tube isolates ventilation when the balloons are inflated, and the longer tube portion is positioned in the right or left mainstem bronchus.
There are certain disadvantages associated with the use of double lumen endotracheal tubes. For example, a double lumen endotracheal tube is larger in outer diameter than a conventional single lumen endotracheal tube, yet its internal cross-sectional area is substantially the same as a single lumen tube. This extended outer diameter can cause damage to the vocal chords, as well as the nerves for the vocal chords. In addition, a larger diameter double lumen endotracheal tube is generally longer, and more challenging to insert and position than a single lumen tube. In patients where the normal airway anatomy is altered, the use of double lumen endotracheal tubes can result in additional patient trauma. Furthermore, due to the complexity and size of a double lumen endotracheal tube, hypoxic brain damage can occur as a result of the length of time that may be required to correctly place the device in the airway. Also, a double lumen endotracheal tube cannot be left in place for long periods of time. Due to its size, extended use of such a tube can cause damage to the tracheal bronchial tree.
Another known medical device for achieving isolation of ventilation is an endobronchial blocker. An endobronchial blocker is a balloon-tipped catheter which is positioned in either the right or left mainstem bronchus using a fiberoptic bronchoscope. When the device is properly positioned, the balloon is inflated to achieve isolation of ventilation. Some endobronchial blockers are not directly coupled to the motion of a fiberoptic bronchoscope. As a result, the operation of the fiberoptic bronchoscope and the balloon-tipped blocker are entirely independent, which can cause difficulty when positioning the blocker. Correct placement of such blockers normally requires several attempts before the device is properly positioned. Some of these devices utilize a removable stiff mandrel wire, placed in the lumen of the blocker, to allow manipulation during placement. The presence of such a wire can cause tissue trauma due to the stiffness of the end portion. In addition, such blockers only incorporate a single lumen in the design. This lumen accepts the removable mandrel wire, and allows inflation of the balloon when the mandrel wire is removed. The single lumen design can prevent gas from being properly aspirated from or added to the blocked section, irrigation fluids from being added to the blocked section, and irrigation fluid, secretions or blood from being removed from the blocked section. In addition, the balloon used with such devices is generally a low volume, low compliance, high pressure, spherical or elliptical balloon. This type of balloon can cause damage by transmitting excessive pressure to the tracheal wall, and it has no mechanism to sense the inflation pressure.
An improved endobronchial blocker is described in U.S. Pat. No. 5,904,648, incorporated by reference herein. The device of the '648 patent is a wire-guided double lumen blocker that has a nylon guide loop extending from a distal end-hole of the tube. The guide loop provides a mechanism to link the endobronchial blocker to a bronchoscope that is used to navigate the sharp bends of the tracheal bronchial tree. As a result, the blocker can be more easily guided to the desired location of a bronchial occlusion than earlier blockers. Following withdrawal of the bronchoscope and the loop, the balloon is inflated to provide obstruction of a portion of the lung from ventilation. This device has been found to be very effective in allowing accurate placement of the endobronchial blocker. However, if the blocker inadvertently becomes disengaged at some point during the medical procedure, it is generally not possible to reinsert the nylon guide loop, since the loop will generally buckle under the pushing reinsertion load. Thus, in order to reposition the blocker, it is necessary to repeat the entire insertion process with a new blocker. Although it would be possible to retain the guide loop in the bronchial mainstem throughout the procedure in order to simplify the possible re-positioning of the blocker, the maintenance of the guide loop occupies space in the lumen that is then not available for other uses, such as providing additional ventilation space to the patient. Thus, it is normally considered good practice to remove the guide loop during the blocking operation.
Yet another commercially available device that has been used to achieve isolation of ventilation is the UNIVENT tube. The UNIVENT tube is a double lumen endotracheal tube that includes a large lumen and a small lumen. The large lumen allows ventilation by conventional means, and the smaller lumen accepts an endobronchial blocker. The endobronchial blocker is advanced into the right or left mainstem bronchus, and the balloon is inflated to achieve isolation of ventilation. The remaining portion of the UNIVENT tube remains in the trachea in the same fashion as a conventional endotracheal tube. A disadvantage associated with the use of the UNIVENT tube is that the endobronchial blocker can be difficult to place, particularly in the left mainstem bronchus which requires that the blocker traverse a sharp angle. The tube should be placed using a fiberoptic bronchoscope; however the motion of the fiberoptic bronchoscope and the blocker are entirely independent. In addition, in clinical practice the UNIVENT tube is generally larger in diameter than a conventional endotracheal tube. This can lead to difficulty in tube placement, and to possible damage to the vocal chords. Furthermore, the ventilation lumen of the UNIVENT tube is smaller in cross-section than that of a similar-sized conventional endotracheal tube. In patients with severe pulmonary disease, this smaller cross-sectional area can make removal of the UNIVENT tube at the conclusion of surgery difficult. The effort involved in breathing through this small lumen is higher, and there is the risk of ventilatory failure.
It would be desired to provide an endobronchial blocking device that may be readily positioned via a fiberoptic bronchoscope in either the right or left mainstem bronchus, that may be used with a single lumen endotracheal tube, and that may be readily re-positioned in the bronchus in the event of dislodgement.